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A block diagram of a bipolar HVDC transmission system, between two stations designated A and B. AC – represents an alternating current network CON – represents a converter valve, either rectifier or inverter, TR represents a power transformer, DCTL is the direct-current transmission line conductor, DCL is a direct-current filter inductor ...
The Cold War period was widely understood as one of bipolarity with the USA and the USSR as the world's two superpowers, whereas the end of the Cold War led to unipolarity with the US as the world's sole superpower in the 1990s and 2000s. Scholars have debated how to characterize the current international system. [2] [3] [4]
In electronics, the Gummel plot is the combined plot of the base and collector electric currents, and , of a bipolar transistor vs. the base–emitter voltage, , on a semi-logarithmic scale. This plot is very useful in device characterization because it reflects on the quality of the emitter–base junction while the base–collector bias, V bc ...
This current is carried by ions present in the atmosphere (generated mainly by cosmic rays in the free troposphere and above, and by radioactivity in the lowest 1km or so). The ions make the air weakly conductive; different locations, and meteorological conditions have different electrical conductivity .
Like most electro-mechanical machines, a homopolar motor is reversible: if the conductor is turned mechanically, then it will operate as a homopolar generator, producing a direct current voltage between the two terminals of the conductor. The direct current produced is an effect of the homopolar nature of the design.
Shorter time scales mostly arise from currents in the ionosphere (ionospheric dynamo region) and magnetosphere, and some changes can be traced to geomagnetic storms or daily variations in currents. Changes over time scales of a year or more mostly reflect changes in the Earth's interior , particularly the iron-rich core .
The use of the bipolar option does not require the placement of a return electrode because the current only passes between tines of the forceps or other bipolar output device. Electrosurgery should only be performed by a physician who has received specific training in this field and who is familiar with the techniques used to prevent burns.
In 1960, M. J. Lighthill criticized the applicability of ideal or resistive MHD theory for plasmas. [12] It concerned the neglect of the "Hall current term" in Ohm's law, a frequent simplification made in magnetic fusion theory. Hall-magnetohydrodynamics (HMHD) takes into account this electric field description of magnetohydrodynamics, and Ohm ...